caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, cacao, and kola nuts and used medicinally as a stimulant and diuretic

Examples of caffeine in a Sentence

Her doctor told her to avoid caffeine.

Recent Examples on the Web

Some people find its caffeine content too strong, while others simply don’t love the taste. —Jillian Kubala, Health, 22 Oct. 2025

Differences in specific genes may cause a person to metabolize caffeine quickly or slowly. —Brittany Lubeck, Verywell Health, 22 Oct. 2025

Meet fellow caffeine lovers, sample local roasts and learn from Cincinnati's supreme latte artists. —Caroline Ritzie, Cincinnati Enquirer, 22 Oct. 2025

Powered by a blend of squalane, ceramides, peptides, and caffeine, this eye cream expertly improves skin’s moisture levels for plumper, bouncier skin. —Conçetta Ciarlo, Vogue, 8 Oct. 2025

Word History

Etymology

German Kaffein, from Kaffee coffee, from French café

First Known Use

circa 1823, in the meaning defined above

Phrases Containing caffeine

• caffeine-free

Rhymes for caffeine

• agin
• alkene
• allene
• ameen
• amin
• amine
• arene
• athene
• baleen
• beeline
• benzene
• between

Kids Definition

caffeine

noun

caf·​feine ka-ˈfēn 

ˈka-ˌfēn

: a bitter stimulating compound found especially in coffee, tea, cacao, and kola nuts

Medical Definition

caffeine

noun

caf·​feine ka-ˈfēn, ˈka-ˌ; ˈkaf-ē-ən 

: a bitter alkaloid C₈H₁₀N₄O₂ found especially in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic

caffeinic

ka-ˈfē-nik  ˌkaf-ē-ˈin-ik 

adjective